The companies will discuss the role they played in Russia’s attempt to influence the US presidential election.

Top lawyers from Facebook, Google, and Twitter will be grilled in Congress next week about the role the companies played in Russia’s attempt to influence the US presidential election.

Their public testimony in front of the House and Senate is expected to paint the most comprehensive picture yet of how Russian government-linked accounts spread divisive messages and fake news to US voters, in an attempt to sway the election in favor of Donald Trump. The companies are also a focus of FBI special counsel Robert Mueller’s probe.

Congressional hearings like this are part education, part political theater—they’re designed to inform US citizens about an ongoing issue, lay out how widespread or problematic it is, and give a sense of how far along the investigation is. Both Congress and the individuals testifying have probably gone through some of the questions privately, but now the answers will be public record.

In recent months, Facebook found 3,000 ads linked to Russian accounts that violated company policy, Twitter has disclosed 200, and Google found ads linked to Russian accounts on YouTube, Gmail, and Google Search products. Russian actors were expert at finding the fault lines in America, and focused on issues like LGBTQ rights, border security, police brutality, and immigration, Congressional aides have said.

Several Congressional aides Quartz spoke to ahead of the hearing emphasized that there’s a growing sense in Congress that there’s no way to entirely regulate away fake news and propaganda—US voters will need to be more skeptical about what they read on the internet. This hearing will make that plain, they said.

What will they be asked?

Congress members want to paint a clear picture of what happened, so expect lots of specifics.

How, exactly, did Russian-linked accounts use these companies?

Who did they target, how much money did they pay, and who saw their posts?

What did they do when they realized there was a problem?

How and when did these companies search for propaganda, and what did they do when they found it?

What are they doing to prevent these problems going forward? Twitter and Facebook have both announced new guidelines for their ad program, but is there more?

What will companies say:

“We’re taking this seriously” is likely to be the main message, as companies try to prove they’re moving fast to identify problem accounts and shut them down.

Members of Congress in both houses have been frustrated by how uncooperative these companies were at first, and how perfunctory they felt their preliminary searches were for Russian-linked users. (That has changed in recent weeks, Congressional aides say.)

Already, Senators have written a bill that would require companies to provide more information about political ads, and companies are eager to prove there’s no need for even more regulation.

“We need your help” may be another message from companies, which have expressed frustration that the FBI and other US investigators identified propaganda on their platforms ahead of the election, but didn’t point it out.

What you won’t hear:

Don’t expect any bombshells connecting the Trump campaign team and the Russian propaganda effort. If it does exist, that sort of sensitive information will be divulged by the FBI when its investigation is finished.